Originally Posted by Maine Sail
Not at all. The point of adequate grounding is to attempt to take the brunt of the strike directly to Earth & not allow it to divert off path and go through your hull... With well bonded boats I simply see less of this:
This does not at all mean the strike won't damage your boat, but it can help to minimize hull-sinking damage..There are no absolutes in lightning strikes all we can do is to attempt to minimize damage and the best way I know is to bond your spar/stays to external lead or an external copper lightning grounding system.
When our boat was hit the lightning exited at the dead bottom of the keel and nowhere else. I know some "lightning experts" say this can't happen but it does.... Our hull was 100% perfect but all electronics were toasted.
Our spar is grounded to the longest J bolt in the keel (our keel has the bolts installed at varying depths with the deepest right under the spar. It is bonded with 2/0 wire.
If you have internal ballast then an option like this can be a good choice if you can keep the wire bends minimal.
My ballast, as an example, is completely encapsulated and not grounded to anything. Water from a hole in the hull down at the ballast does not get into the bilge anyway. I have proven this:-) All my metal parts are bonded well with what looks like #6 stranded copper back to a sintered plate by the engine. I think the bonding idea makes a lot of sense (if anything does in this lightning topic) in that if your boat and the surrounding sea all have similar electrical potential, lightning has less reason to be attracted to your mast any more than to the surrounding area as the shortest route to ground. Under those parameters, lightning has almost the same chance of hitting 50' from your boat as it does striking the boat. That is what the grounding system does more than attracting lightning to a safer route through your boat. Lightning is trying to get to GROUND, not the water. If the boat looks like the rest of the water, it has less reason to target the boat. The mast is a better conductor than air so the closer it can be to the potential of the sea, the better. Anyway, although counter intuitive, that's the way I've heard the grounding idea explained. If you have contradictory theories about this, would like to hear them. Once lightning actually makes a direct hit, all bets are off and you're just lucky if it doesn't travel in a direction which burns a big hole in the fg.